I have no doubt that O'shea can scheme a guy open, but those plays take time to develop, as a rule. Fitz doesn't usually have time to wait with a vitually unabated pass rush in his face.
Yup. If I'm DC, I'm going to find a way to get quick pressure. DVP and MG are dangerous on those mid to deep passes.
That's why Wilson (or someone similar) is a need.